Automatically reclosing circuit interrupter



Oct. 24, 1944. R LUDwlG ETAL 2,361,221

ATOMATI-CALLY REcLosING CIRCUIT INTERRUPTER Filed March 5, 1942 ATTORNexcessive value.

Patented oct. 24, '1944 AUTOMATICLLY RECLOSING CIRCUIT INTERRUPTER Leon-R.. Ludwig, Wilkinslmrg, Pa., and John W. May, Durham, N. C., assignorsto Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,a corporation of Pennsylvania Application March 5, 19.42, serial No.433,472

4 Claims.

Our invention relates to circuit interrupters, and in particular relatesto automatically reclosing circuit breakers.

For certain purposes such, for example, as rural electrication, it isdesirable to have a circuit interrupter which will automatically open`when excessive current iiows through the line,

, and will then automatically reclose itself after a short interval,since in many cases the cause `of the short circuit disappears within atime if the line is disconnected from a source of power.

f It is, however, impossible to be certain that the cause oftheexcessive current or short circuit' will be removed merely by a briefremoval of the line from connection to the voltage source, and in suchcases it isde'sirable that the circuit breaker shall again automaticallyreopen this circuit as soon as the load current reaches an In someinstances, -a second or a third interruption of the connection betweenthe line and the voltage source will be followed by a disappearance ofthe condition causing excessive current ilow, but there are occasionalsituations in which excessive current will flow even after aconsiderable number of reclosures of the circuit breaker connecting theline to the voltage source. Such a repeated opening and reclosure of thecircuit interrupter will quickly overheat and ruin the latter, and itis, accordingly, desirable to provide an arrangement by which thecircuit breaker shall remain open if the cause of excessive current doesnot disappear v after a few automatic reclosures.

Our invention relates to a novel arrangement for thus Yopening andreclosing a circuit breaker when the line carries excessive current, butwill carry out this operation for only a limited number of reclosuresand thereafter maintain` the circuit breaker open permanently until itis manually reclosed by a power-line attendant. It is an improvementupon the circuit interrupter shown in John W. Mays application SerialNo. 423,631, led. on or about December 19, 1941, for Automaticallyreclosing circuit interrupters, assigned to the Westinghouse Electric cManufaclturing Company of East Pittsburgh, Pennsylvania.

Circuit interrupters for carrying out the abovementioned function havebeen devised before, but

there are certain special conditions characteristic of ruralelectriflcation and' other similar ilelds which make prior art .circuitbreakers unsatisfactory; for example, by reason of their excessive costcompared with the service they are expected to render, or theirmechanical complexity or their liability to require constant inspectionand repair or their short life' in service. The device which we haveinvented avoids such diixculties as have just been enumerated, inasmuchas it has a relatively low iirst cost, has no complicated gear trainescapements, ratchets or similar complex mechanisms, has few movingparts likely to get out of order, and -is adapted to employ standardcircuit interrupters which have been developed for non-reelosingcircuits and which are now marketed in large numbers at very low costand with high reliability.

One object of our invention, accordingly, is to provide a circuitinterrupter which shall reclose automatically, but for only a limitednumber of times, and shall then remain open circuited.

' Another object of o ur invention is to provide an arrangement of thetype mentioned in the preceding paragraph which shall employ for itscircuit interrupting, function mechanisms which have been developed andsuccessfully used for non-reclosing circuit breaker service.`

Still another object of our invention is to provide a circuitinterrupter of the type mentioned under the rst paragraph naming theobjects o f our invention which shall be inexpensive to manufacture, andwhich shall employ a minimum of moving `parts and other mechanicaladjuncts.

-Still another object of our invention is to provide an arrangement ofthe type mentioned in the iirst paragraph naming the objects of ourinvention which shall employ two diierently rated bimetallic orthermostatic elements for controlling the tripping and reclosing cyclesof the circuit breaker.

Still another object of our invention is to provide an arrangementmentioned in the immediately preceding paragraph in which is embodied atripping coil which is traversed by substantialV the first paragraphnaming the objects of our invention in which the arrangement controllingthe opening and reclosingv cycle has an inverse time-currentcharacteristic andcan be altered.

as vto rating very simply by replacement of only two relativelyinexpensive and simple bimetallic elements of the device.

Still another object of our invention -is to provide an improvedarrangement for energizing a principles of our invention;

Fig. 2 is an enlarged sectional view in the direction II-II of theopening solenoid structure shown in Fig. 1; and

Fig. 3 is a schematic diagram of connections of the opening solenoidcircuit.

Referring in detail to the drawing, the circuit interrupter. ispreferably contained within an enclosure or tank I which may be ofinsulating material or may be of suitable metal. Line terminals for thecircuit controlled by the circuit interrupter are mounted at 2 and 3 onthe casing I, each line being preferably insulated from the casing ifthe latter is of metal by washers 4, 5. The terminal 3 is connected-by athrough-bolt 3, insulated from the casing I if the latter is -ofmetal,'with one layer 1 of a thermostatic bimetal which carries on itsfree end the holding element 3 of a latch, the other element 9 ofwhichrevolves about a stationary pivot II and constitutes thetripfree arm ofthe so-calied tripfree mechanism of a circuit breaker actuatingarrangement such as that shown in Patent i 2,044,157, issued June 16,1936 to H. D. Dorfman et al., and assigned to' Westinghouse Electric &Manufacturing Company, the assignee of our instant application. Thelayer I2 associated with the above-mentioned layer 1 to constitute abimetallic thermostatic element is insulated from the layer 1, except atthe free end of the bimetal, as a result of which current owing from theterminal 3 traverses the layer 1 to its free end and then ows backthrough the layer I2 to the ilexible lead I3 which conducts current tothe moving contact I4 of the circuit breaker mechanlsm illustrated inthe above-mentioned patent. The stationary contact I5 of the circuitbreaker mechanism is mounted on circuit breaker base plate of insulatingmaterial and current flows thence through the strap I1 to the ilxed endI3 of a second bimetallic thermostatic element I3. Current then ilowsthrough the second thermostatic element to the free end thereof, thenceflowing through a contact button 2I to a second contact button 22 whichis normally in contact with the button 2l in the undeected condition ofthe ,bmetallic element now under discussion.

The contact button 22 is mounted in a fixed position on an insulatingblock 23 which is supported from the wall of the enclosure I. A ilexiblelead 24 extends from the contact button 2I to one terminal of a solenoidenergizing arrangement which is mounted on the casing I and which isshown in more detail in Figs. 2 and 3 and described iully below. 'I'heother terminal of this solenoid arrangement is connected through a lead23 with the terminal 2. 'I'he contact button 22 is also connected by asuitable lead passing through the wall of the container I to theterminal 2. i

The operating mechanism for the movable contact I4 comprises a lever 21having a stationary pivot 28 and kattached to-the-resilient arm 23 whichsupports the contact I4.

riveted to the '1 5 lever 21 is a link 3| which is, in turn, pivoted toone end of a link 32 of which the other end` is pivoted upon the arm 3.The links 3l and 32 constitutes. toggle arranged for stability in theposition shown in the drawing, in which the movable contact I4 ispressed into iirm engagement with the stationary contact I3.

A handle 33 having a stationary pivot 34 is connected to the knee of thetoggle 3I, 32 by a spring 33 which in the position shown in the drawingexerts a force on the knee of the toggle 3l, 32 to hold it in theposition shown, thereby stressing the contacts I4, I3 to closed circuitposition. The handle 33 may, however, be turned counterclockwise aboutthe pivot 34 thereby displacing the upper end of the spring 33 downwardin the drawing to such a degree as to pull the knee o! the toggle 3|, 32likewise downward, thereby breaking the toggle and pulling the movablecontact I4 away from the stationary contact I3. The free end oi thehandle 33 is biased in a clockwise direction in the drawing by a-spring33 which is attached to an insulating projection 31 attached to thestrap I1. The handle 33 carries an arm 33A adapted to engage thetrip-free arm 3 under certain conditions later to be explained. In amultipole circuit breaker each pole comprises the elements so farenumerated.

The handle 33 is adapted to bemoved i'roml its closed circuit position,as shown in the drawing, and against the bias of the spring 33 by a bellcrank lever 33 pivoted at 33 to the container I. In a multipole breakerthe arms 33 of the respective poles are mechanically linked to move inunison. 'I'he bell crank lever 33 is moved clockwise from the positionshown in the drawing by a magnetic core 4I which slides through the axisof the solenoid arrangement above mentioned. The core 4I is providedwith a handle 42 by which it may be moved manually. There is provided arod 43 which slides through a guide 43 and has its end pivoted tobimetal I3. When the latter is heat-deflected by being traversed byoverload current, it moves the end of the rod 43 downward into latchingengagement with core 4I for a purpose to -be described below., A singlebell-crank lever 33 and core 4I suilice even for a -multipole breaker.

The solenoid arrangement mentioned above is shown in elevation in Fig. 1at 23, and Fig. 2 shows a view along the plane II-II of Fig. 1. The mainsolenoid encloses and attracts the core 4I and consists of one winding43 for each pole of the circuit'interrupter. The windings are mounted onan iron magnetic circuit 41 which may be of the shell type well known inthe solenoid art. Mounted on one side oi' this magnetic circuit 41 is aseries of hinged armatures 3i, one for each pole of the circuit breaker(a three-pole breaker being shown as an example) each armaturecooperating with a magnetic circuit comprising a pole piece 34 and aportion of the above-mentioned magnetic circuit 41. There is aprojecting pole piece 54 for each pole of the circuit breaker, and eachsuch pole piece is surrounded 4by an auxiliary solenoid 33 which isconnected to the lead 24, already described, corresponding to theassociated pole of the circuit breaker. Each of the armatures 3| carriesa movable contact 36, which is biased into engagement with a stationarycontact 31 by a spring 33. The stationary contact 31 is connectedthrough the lead 23, already described, to the vline terminal 2. Thesolenoid winding 43, corresponding to the assoaannam ciated pole of thecircuit breaker, is connected in shunt across the contacts 56, 51.

The diagram in Fig, 3 shows schematically the connections of thesolenoid arrangement just described. When normal current flows throughthe circuit breaker, the bimetal I9 remains deected to such a smallextent that contacts 2| and 22 are closed and contacts 56 and 51 areretained in closed position by the spring '58. `The main line current,accordingly, divides between the contacts 2|, 22 as one path and a pathcomprising the solenoid 55 and the contacts 56, 51. The strength of thespring 58 is adjusted to such a value that the fraction of the currentilowing through the solenoid 55 is insumcient to move the armature I. Ifnow the current through the circuit breaker rises to a value higher thannormal, the bimetal I9 is soon deflected sufiiciently to open thecontacts 2|, 22, thereby sending the entire line current through thesolenoid 65 and the closed contacts 56, 51. The spring 58 is so adjustedthat with full load current flowing thus through the solenoid 55,contacts 56, 51 are opened, thereby sending the entire line currentthrough the mainsolenoid winding 46, so attracting the core 4 I.

The mode of operation of our above described circuit interrupter is asfollows: Assuming the mechanism to be in the position shown in thedrawing, the contacts I4, I5 will remain in their indicatedclosed-circuit position until sufiicient current ows through the bimetalI9 to separate the contacts 2|, 22 whereupon .the solenoid arrangementwill attract core 4I as already described. The core 4| will be drawninward, thereby rotating the bell crank lever 38 in a clockwisedirection, displacing the handle 33 in a counterclockwise directionagainst the bias of spring 36 and causing the spring 35 to exert a pullupon the toggle 3|, 32 to break the latter, thereby separating thecontacts I4, I5 and opening the circuit. The bimetal 1, I2 will, ofcourse, be heated by this same current but is so proportioned that it isnot sufficiently heated to 'be substantially displaced from the positionindicated in the drawing by the time the bimetal I9 has moved to openthe contact 2|, 22. Opening of the main contacts I4, I5 -of course cutsoil' current flow through bimetal I9, solenoid 55 and solenoid 46 thusreturning the solenoid arrangement to its initial deenergized condition.

The core 4I will remain latched by the rod 43, thus lholding the handle33 in the open-circuit position against the bias of the spring 36, untilsuch time as the bimetal I9 has had time and close the contacts 2|, 22.As soon as the contacts 2|, 22 close, the rod 43 disengages core 4| andthe spring 36 `can pull the circuit breaker handle 33 together with itsattendant bell crank lever 38 and core 4I to the closed circuit positionshown in the drawing. The contacts I4 and I5 are thus again closed.

If during the open-circuit interval just described, the cause of theflow of excessive current through the circuit breaker `has been removed,the circuit breaker will remain in its closed-circuit position. However,if the line is in such a condition that an excessive current still flowsthrough the bimetal I9, the latter will be heated sufficiently to openthe contacts 2|, 22, thereby reenergzing solenoid arrangement 25 toagain pull the handle 33 to the open circuit position against the biasof spring 36. The bimetal 1, I2 is so designed that it is more massivethan the bimetal I9, and hence does'not lose such heat to cool as waspreviously stored in it at the time the circuit breaker was rst opened.The bimetal 1, I2 is, therefore, again heated and caused to store Amoreheat while the circuit breaker remains closed for the short timerequired to heat the bif metal I9 enough to open contacts 2|, 22. Thebimetal 1, I2 is, however, so designed that even after this secondheating, it is not deflected far enough to disengage the latch member 8from the trip free arm 9.

CessationA of current ow through the circuit breaker due to the openingof contacts I4, I5 for the second time again permits the bimetal I9 tocool, thereby disengaging latch 43 from core 4I so that the spring 36can again move the circuit breaker to its closed circuit position. Ifthe cause for excessive current-flow in the line has disappeared duringthis second open circuit interval, the circuit breaker will remainclosed. On the other hand, if the cause of excessive current in the linestill persists, the bimetal 1, I2 is so designedlthat the additionalheating due to the now of this excessive current for the third time willdeflect its upper end to disengage the latch member 8 from the arm 9.When this happens, the spring 35 exerts such an upward pull on the kneeof the toggle 3|, 32 as to move the member 9 clockwise about thestationary pivot II, thereby permitting the arm 21 to rotate about itspivot 28 to open the contacts I4, I5. Thisclockwise movement of member 9is arrested when it engages arm 33A. The circuit breaker will thereafterremain in its `open circuit position regardless of the cooling of thebimetal 1, I2 and the bimetal I9 until an attendant manually moves thehandle 42 to actuate handle 33 to open circuit position through theagency of 'bell-crank lever 38. When this happens arm 33A engages andmoves trip free arm 9 counterclockwise about its pivot II into latchingengagement with the latch member 8. Thereafter, the spring 36 is able tomove the arm 33, the toggle 3|, 32 and the contacts I4, I5 to theirclosed circuit position again as soon as the attendant releases handie42.

It will be recognized that'by properly proportioning the heat-storageand other properties of bimetals 1, I2 and I9 the number of openings ofthe circuit-breaker by bimetal I9 which intervene before bimetal 1, I2unlatches the trip-free arm 9 can be fixed at will. While we have shownthe bimetal I9 as posi-4 tioned above the surface of the oil and thebimetal 1, I2 below the surface of the oil, it will be recognized thatit may, under certain circumstances, be desirable to locate the bimetalI9 likewise below the surface of the oil in the container I. While wehave shown a particular mechanism for moving the contacts I4, I5 toclosed-circuit and open-circuit position, it will be recognized that theprinciples of our invention are by no means limited to the use of thisparticular mechanism in combination with the bimetal 1, I2 and I9. Anycircuit breaker arrangements in which a motor means energized by onebimetal moves to open-circuit position a circuit breaker biased toclosed-circuit position, and in which a predetermined amplitude ofmovement of a second bimetal serves to permit the exertion of forcesable to openy the circuit breaker against any closed-circuit bias actingthereon are within the purview of our invention. The arrangement inwhich the second bimetal releases the trip-free arm of a togglemechanism is, however, a very convenient and advantageous form of ourinvention, which may be used with numerous types of circuit breakermechanism otherwise dissimilar to the specific form shown in the Dorfmanet al. Patent 2,044,157.

Many forms of circuit breaker mechanism having trip-free arm-latches areknown, and the control of the trip-free arm-latch by means oi' a bimetalwhich is only moved sufficiently to unlatch the arm after severalsuccessive trippings of the circuit breaker within a predeterminedlimited interval of time are within the purview of our invention.

We claim as our invention:

l. In combination with a circuit interrupter having its separablecontacts normally biased to closed circuit position, a rst pair ofauxiliary contacts, means to open said auxiliary contacts in response tooverload current through said separable contacts, a magnetic corearranged when moved to actuate said separable contacts to theopen-circuit position, a solenoid winding provided with means forenergizing it and positioned when energized to move said core to opensaid separable contacts, a second pair of auxiliary contacts forcontrolling the energization of said solenoid, an auxiliary solenoidconnected in shunt with said iirst pair ci auxiliary contacts, and meansfor causing energization of said auxiliary solenoid to actuate saidsecond pair of auxiliary contacts after said rst pair of auxiliarycontacts have been operated.

2. In combination with a circuit interrupter having its separablecontacts normally biased to closed circuit position, a irst pair oi.'auxiliary contacts, means to open said auxiliary contacts in response tooverload current through said separable contacts, a magnetic corearranged when moved to actuate said separable contacts to theopen-circuit position, a solenoid winding provided with means forenergizing it and positioned when energized to move said core to opensaid separable contacts, means including a second pair of auxiliarycontacts connected in a shunt circuit which when closed deenergizes saidsolenoid, an auxiliary solenoid connected in shunt with said rst pair ofauxiliary contacts, a magnetic circuit for the mst-mentioned solenoid, amovable armature and pole piece mounted on said magnetic circuit, saidpole piece being arranged to be magnetized by current flow in saidauxiliary solenoid, one member of said second pair of auxiliary contactsbeing mounted on said armature and moved to open position when saidamature is attracted by energization of said auxiliary solenoid aftersaid rst pair or auxiliary contacts have been operated. y

3. In combination with a circuit interrupter having its separablecontacts normally biased to closed-circuit position, a nrst pair ofauxiliary contacts connected to a bimetal traversed by the currentthrough said separable contacts and arranged to be opened when saidbimetal is heated to a predetermined temperature, a magnetic corearranged when moving to actuate said separable contacts to theopen-circuit position, a solenoid winding provided with means forenergizing it and positioned when energized to move said core to opensaid separable contacts, means including a second pair of auxiliarycontacts connected in a shunt circuit which when closed deenergizes saidsolenoid, an auxiliary solenoid connected in shunt with said ilrst pairof auxiliary contacts. and means for causing energization of saidauxiliary solenoid to open said second pair of auxiliary contacts aftersaid first pair of auxiliary contacts have been operated.

4. In combination with a circuit interrupter having its separablecontacts normally biased to closed-circuit position, a rst pair ofauxiliary contacts connected to a bimetal traversed by the currentthrough said separable contacts and arranged to be opened when saidbimetal is heated to a predetermined temperature, a magnetic corearranged when moved to actuate said separable contacts to theopen-circuit position, a solenoid Winding provided with means forenergizing it and positioned when energized to move said core to opensaid separable contacts, means including a second pair of auxiliarycontacts connected in a shunt circuit which when closed deenergizes saidsolenoid, an auxiliary solenoid connected in shunt with said iirst pairof auxiliary contacts, a magnetic circuit for the first-mentionedsolenoid, a movable armature and pole piece mounted on said magneticcircuit, said pole piece being arranged to be magnetized by current nowin said auxiliary solenoid, one member of said second pair of auxiliarycontacts being mounted on said armature and moved to open position whensaid armature is attracted by energization of said auxiliary solenoidafter said first pair of auxiliary contacts 'nave been operated.

LEON R. LUDWIG. JOHN W. MAY.

